Recent Development of Piezoelectric Fast Tool Servo (FTS) for Precision Machining

With an increasing demand of photoelectric components, the micro/ultraprecision machining technology has become more and more important. However, for some particular applications such as micro lens array for light emitting device, head-up display for windscreen of a car, and compensation lens for laser light, etc., those manufactures require the so-called fast tool servo (FTS) or slow tool servo (STS) technology. Different to the STS, the FTS is to employ an auxiliary device of tool holder incorporating with the machine tool. In this review article, an overview of FTS is provided. In the beginning, the classifications of FTS based on motion- and actuator-type are presented. Practical FTSs constructed by piezoelectric, electromagnetic, and magnetostrictive actuators are described. Then, the content is expanded to the piezoelectric FTS including its main components, characteristics of piezoelectric actuator, displacement amplification mechanisms based on flexure hinge, multiple-actuator, hydraulic bellows-type, and hybrid-actuator. In addition to the applications of micro/ultraprecision machining conducted by the STS, the piezoelectric FTS that can provide further unique applications such as non-axisymmetric aspheric machining, on-machine measurement, vibration-assisted machining, axis error compensation, and active vibration control are addressed. Moreover, the control strategies for the piezoelectric FTS are introduced, and the progress of multi-axis piezoelectric FTS is described. Finally, the challenges and perspective of the FTS are mentioned, and a conclusion is made. Through this article, the fundamental knowledge of FTS can be acquired. This is helpful in further developments and practical applications of FTS.